Properties of fly ash-FGD gypsum-lime based products

Abstract

Bricks were produced by using six different combinations of fly ash, flue gas desulphurization gypsum and lime with the addition of 10 wt% water. The products were shaped by means of pressure forming process. The bricks were subjected to steam curing for 6 and 10 hours and then, moist cured until being tested. The compressive strength tests were conducted at the ages of 3, 7, and 28 days and 24-hour water absorption tests were performed on the products aged for 28 days. Results showed that steam curing duration influenced the compressive strength values of the bricks at mostly early ages. It was also found that increase in the lime content generally improved the 28-days compressive strength values. However, at early ages, the specimens with high gypsum content were stronger. It was realised that the water absorptions generally decreased with the increase in lime content. Moreover, as it was expected, steam curing time affected the water absorption properties positively. At the end of the study, it was concluded that the solid by-products such as fly ash and flue gas desulphurisation gypsum of thermal power plants can be utitised as brick making materials through a pressure forming process.